The BackShade property contains a numeric expression that can be used to darken the theme color in the BackColor property. The default value of the BackShade property is 100, which is neutral, and does not change the theme color. To darken the color, first determine the percentage by which to darken from 1 to 100, then subtract that value as a whole number from 100 and use the remainder. For example, to darken the theme color by 75%, subtract 75 from 100 and use the remainder, which is 25.